1. Field of the Invention
The present invention relates to filters for liquids. More particularly, the present invention is directed to an internal filter for use in the water circulation systems of conventional pools or spas.
2. Description of the Prior Art
Filters of various configurations are known in the art for use in swimming pools, spas, and the like in order to remove solid particles and debris from the circulated water. Such filters are typically mounted in-line within the pool or spa circulation system and are configured with a liquid-permeable filter media such that when the circulation system is in operation, the water can be pulled through the filter and pumped back into the pool or spa, leaving the captured debris on the filter for subsequent removal.
The conventional cartridge filter as is known and used in the art is generally comprised of a cylindrical filter element having one or more layers or sheets of a porous material configured with a pore size to allow the passage of water while trapping and removing the solid particles from the water that are unable to pass through the pores. As the filter traps more and more solid particles, the pores in the filter media become clogged, inhibiting the flow of water through the pool or spa""s circulation system and thereby decreasing performance and possibly even damaging the circulation pump. In an attempt to address these concerns, the cartridge filters known in the art typically employ relatively large sheets of the porous filter material that are pleated so as to provide an increased filter surface area, thus increasing the life and performance of the filter, while not increasing the filter""s overall size. The filter material is maintained in its cylindrical, pleated configuration by being mounted on a rigid cylindrical core and capped on each end by an annular end cap.
Though the conventional cartridge filter is in wide use, there are still several shortcomings with this filter type that have not yet been overcome. First, the flow rate through the cartridge filter is limited by the material and configuration of the pleats and the apertures in the rigid cylindrical core. Such flow rate is typically on the order of 100 gpm when the filter is new. Second, despite the overall increased surface area of the filter material achieved by the pleats, only so much of this surface area is truly usable, as the folds of the pleat are tight and are butted up against the cylindrical core. Moreover, as particles and debris become lodged between the pleats, the useful filter surface area that is lost is effectively doubled because the particles and debris clog pores on both adjacent surfaces of the pleat. Thus, cartridge filters become clogged and experience decreased flow rates relatively quickly. A third shortcoming of the cartridge filters known and used in the art is that they cannot be readily cleaned after becoming clogged. In the interest of increasing the total filter surface area, the pleats of the typical cartridge filter are numerous and densely configured about the filter""s circumference. Thus, in order to remove the debris trapped deep within the pleat folds, high pressure reverse flow or meticulous debris removal using a vacuum or manual technique between each pleat is necessary. It is further recommended that the cartridge be soaked overnight in a cartridge cleaning solution and then be thoroughly cleaned a second time before being returned to use. Because of these inconveniences, some pool and spa owners simply use their cartridge filters until they become clogged and discard them, often prematurely, rather than bothering to clean them out. Moreover, because cartridge filters trap debris on the outside of the filter only, when the filter is removed from the pool or spa for cleaning or disposal, it is possible that the debris that is loose and easily removed will fall off the filter into the clean side of the circulation system rather than being permanently removed.
For these reasons, other pool and spa filters have been proposed in the art. Diatomaceous earth (xe2x80x9cDExe2x80x9d) filters house internal, parallel grids made of extremely fine mesh that is coated with DE, which is crushed, petrified bone that acts as an adhesive and traps particles and debris from the water as it is filtered through the layers of DE grids. These DE filters are relatively more expensive than comparable cartridge filters and may be subject to municipal or environmental authority regulations pertaining to cleaning and disposal. Similarly, sand filters have also been proposed that essentially use a sand and gravel filter medium that mixes with the circulated water as it passes through the filter to pull out dirt and debris. However, the debris is not permanently captured by the sand filter medium and can eventually work its way through the filter and back into the pool or spa circulation system. It has been proposed that an additional solution be added to the sand to coagulate the particles and debris being filtered into larger clumps that can be more easily trapped by the sand filter medium. As a further maintenance step with sand filters, periodically, the sand itself is depleted from the filter and more sand of a specific type must be added. Sand filters, like the DE filters, are more costly than cartridge filters.
Bag-type filters for separation of unwanted solids from liquid process flows have also been employed in various industrial filtration applications in the interest of increasing flow rate and efficiency. To this end, filter assemblies having bag filters supported on rigid structures or stiffening frames and having elaborate sealing arrangements between the filter and the surrounding housing have been proposed. For example, U.S. Pat. No. 4,769,052 to Kowalski is directed to a flexible fabric filter bag apparatus having multiple support surfaces. A double-walled, porous cylinder cooperates with a stretching frame to suspend and support the filter bag within a rigid cylindrical outer housing. An annular flange is provided in the housing""s inner wall and is configured to sealingly engage a metal ring within the bag""s open end when the bag, the double-walled cylinder, and the stretching frame are positioned inside the outer housing. A cover is installed over the open end of the outer housing to seal the filter and to force the stretching frame downwardly to draw the filter bag taut against the surfaces of the double-walled support cylinder.
U.S. Pat. No. 5,910,247 to Outterside is directed to a similar filter bag system. Like the Kowalski filter apparatus, Outterside discloses essentially a double-walled filter support cylinder, consisting of an outer basket and an inner tubular member, a housing having a lid for sealing the filter, and a filter bag having a ring in its open end to sealingly engage a flange on the basket. Outterside further discloses specific dimensions for the filter bag which purportedly maximize the surface area without restricting the process flow rate. Moreover, the Outterside system""s supporting structures are configured to prevent collapse of the filter bag when the process flow is reversed to backwash and clean the filter without removing it. Hence, it is essential that the filter bag fit snugly and securely over the outer basket and inner tubular member. To this end, Outterside discloses that the filter body is smaller in diameter than the outside diameter of the tubular support member so that the filter must be stretched to fit over the tubular body and is retained thereon through a frictional fit.
Therefore, the bag filters known and used in the prior art essentially entail a multi-walled support structure that may further include additional stretching or stiffening frames, a filter bag that is secured on the support structure and shaped by the alternative frames, and a filter housing, or vessel, that contains the filter bag assembly and provides for a positive seal between the xe2x80x9cdirtyxe2x80x9d and xe2x80x9ccleanxe2x80x9d side of the filter along a ring integral to the bag""s open end. Based on the configuration and number of components in these prior art industrial bag-type filters, it follows that such filters are not well-suited for use in spas because of their complex design and inherent relatively high cost. Furthermore, the housing, which plays a critical role in the function and performance of the prior art bag-type filters, is particularly ill-suited for use in a spa""s circulation system because the conventional spa""s filter-receiving cavity cannot accommodate the housing, and the housing itself, having only one small inlet strategically positioned above the location where the filter is sealed within the housing, would likely perform poorly under the changing water levels and other conditions of a pool or spa during use.
Thus, there exists a need for an inexpensive, convenient, and functionally efficient filter for use in spas and the like that is both easily reusable and disposable.
The present invention is directed to an internal spa filter including a filter body and a complementary filter bag having a sheath which encompasses the exterior of the filter body and an internal pocket which extends into the filter body. The filter body is configured to be installed within a spa""s water circulation system in order to filter particles and debris out of the water. As the spa water is circulated, through the filter body a vortex effect is created within the filter bag pocket trapping debris therein for later removal without the risk of the debris falling off the filter and back into the spa water. The configuration and materials of the spa filter of the present invention, as compared to the prior art filters, provide for much higher flow rates through the filter, further enhancing both the performance and life of the pump of the spa circulation system. Moreover, the spa filter of the present invention is relatively inexpensive to manufacture, whereby, after prolonged use, the filter bag itself may be either readily cleaned and reused or alternatively simply discarded.
The filter body of the spa filter of the present invention is defined by a cylinder having a spa water opening at its inlet end and a spa water discharge orifice at its opposite end. Throughout the filter body""s cylindrical wall is formed, a pattern of auxiliary spa water inlet openings. The inlet and auxiliary openings permit the passage of the circulated spa water from the outside of the filter body to the inside thereof. The sheath of the filter bag is joined to the pocket thereof along a circumferential inseam. Accordingly, when the bag is placed about the filter body, the closed end of the pocket is inserted within the filter body""s open end while the sheath encompasses the outside surface of the filter body""s cylindrical wall, with the inseam of the filter bag positioned substantially along the inlet edge of the cylindrical wall""s inlet end to maintain the position of the filter bag on the supporting filter body. The pocket extends towards the discharge end of the filter body.
One embodiment of the filter body utilizes a cylinder, the sides of which are formed with a pattern of round through-hole openings preferably having a nominal diameter of 0.60xe2x80x3. For a cylinder having an outside diameter of approximately 5xc2xd and a length of approximately 8xe2x80x3, sixteen such holes are radially-spaced apart in each of six parallel, circumferential rows in the wall to yield a total of ninety-six through holes generally spaced uniformly throughout the wall. In an alternative filter body embodiment, a mesh-type pattern is formed in the cylinder sidewall having a pattern of small, square apertures throughout the wall arranged in spaced-apart relationship about parallel circumferential rows substantially throughout the wall. Because the square apertures are relatively smaller than the through-hole apertures of the first embodiment, for the same overall dimensions of the wall, the number of square apertures and the number of rows are significantly increased, yielding a total of more than two-thousand square apertures. A third embodiment of the filter body of the present invention has lengthwise axially extending slots formed about its circumference.
In each embodiment of the filter body, the body includes an open inlet end about which the filter bag sheath is draped and an opposite rear closed discharge end formed by a rear wall integral with the rear end of the filter body and generally normal to the axis of the filter body. A central circular discharge orifice is provided in the wall for discharge of the flow of the spa water entering the filter body through the filter bag. A length of tubing extends from the discharge orifice normal to the rear wall and projecting axially away from the filter body. The tubing is configured with external threads for threadably engaging piping of the spa""s circulation system. Preferably, the filter body will be positioned vertically within a filer-receiving bag of the spa with the inlet end of the cylinder disposed above the discharge end thereof so that water from the tub of the spa is drawn downwardly through the filter body to the suction end of the spa""s pump. The filter body may be constructed of a thermoplastic material such as polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), or acrylonitrile butadiene styrene (ABS). These materials are readily available, are relatively inexpensive, and are easily processed using injection molding and finishing techniques known in the art.
The filter bag of the present invention includes a support ring at the juncture of the sheath and pocket along a circumferential inseam formed by looping the upper end of the pocket over the upper end of the sheath to form a loop or circumferential cavity. The support ring preferably has a nominal diameter substantially equivalent to the nominal diameter of the filter body so as to be positioned adjacent the upper end of the filter body when the filter bag is placed on the filter body, thereby maintaining the filter bag in position and keeping the pocket open during use. To this end, the support ring is to be constructed of any suitable rigid or semi-rigid material such as a thermoplastic material or stainless steel. To maintain the position of the support ring within the circumferential cavity and to secure the inseam, stitching, welding, stapling or other fabric attachment means known in the art are employed.
A removal handle spans the open upper end of the filter bag pocket and is attached at two opposite locations. The handle may be stitched, welded, or otherwise joined to the filter bag using any attaching means known in the art, but is preferably attached within the inseam itself. The length of the handle is sufficient to loosely span the pocket opening, so that the handle may droop within the pocket when not in use and may be pulled up for convenient access when the handle is to be grasped to remove the filter bag from the filter body.
The filter bag of the present invention may be constructed of a durable, porous, fibrous material known in the art for use in various filtration applications. Though many types of fabrics may be used in fluid filtration to effectively remove debris and particulate matter while allowing the fluid itself to pass through the filter media, in a preferred embodiment, the material selected will have a porosity rating of 40 to 50 microns and have a weight on the order of 12 oz/yd2. Examples of suitable materials include polypropylene (PP), polyethylene (PE), polyester felt, or fiberglass. The handle may be made of the same material as the sheath and the pocket or may be made of a conventional cotton and polyester textile material.
In operation, after the sheath of the filter bag has been removably positioned in covering relationship over the filter body with the bag pocket extending into the filter body, the internal spa filter of the present invention is ready for use and is installed within the filter-receiving bay of a conventional spa with the filter in direct communication with the spa""s circulation system on the suction side of the pump. Once the spa tub is filled with water and the circulation system is operated, the water is drawn through the filter by the pump. Because the inlet opening of the filter bag, approximately 5xc2xd diameter, is relatively larger than the discharge orifice at the closed end of the filter body, which is typically on the order of 1xc2xd, this difference in area will naturally create a vortex tending to draw the water down through the filter pocket, pulling larger debris into the pocket and trapping it there for later removal. The vortex action and the resulting strong suction of water through the filter also creates a vacuum pressure on the inside of the filter that serves to pull the filter bag""s sheath tightly against the exterior of the filter body, thus effectively creating a tight fit between the sheath and the filter body which causes all water being pulled through the filter to pass through the filter bag.
The porosity of the filter bag material, the configuration of the open pocket, and the vortex effect cooperate to provide for higher flow rates through the filter (on the order of about 150 gallons per minute) as compared to conventional prior art spa filters. This increased flow rate translates to enhanced performance of the spa in terms of the relaxation and therapeutic benefits to the user and the life of the circulation pump.
When the filter bag of the present invention has become sufficiently dirty that it should be cleaned or replaced, the spa""s circulation system is shut down and the filter bag is simply lifted out of the filter body by grasping the handle. The debris trapped by the filter during use will remain within the inside pocket, thereby not contaminating the spa water as the filter bag is removed from the filter-receiving bay. If the filter bag is removed from the spa to be cleaned for reuse, the bag is dumped or rinsed out to remove all debris that has been trapped or alternatively may be washed or laundered in a conventional washing machine and dryer to more thoroughly clean and sanitize the bag. If it is preferred that the filter bag be replaced rather than being cleaned, the used filter bag may be simply discarded and a new bag put into the filter body. Because the materials and construction methods employed in producing the filter of the present invention are relatively inexpensive, disposing of the filter bag is both a convenient and economical it cleaning the bag.
Other features and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the features of the invention.